The invention relates to a rotatable magnetic head assembly for use in a magnetic tape recording/playback apparatus of a type in which the magnetic tape is wound around the assembly over such an angle as to enable the apparatus to operate in a helical scanning recording/playback mode. Such an assembly includes a rotatable supporting member which supports two diametrically oppositely located magnetic heads each of which has two subheads having mutually parallel transducing gaps which are positioned so as to form on the magnetic tape simultaneously two oblique tracks having a certain intermediate space. Between two tracks which are formed simultaneously by one of the two magnetic heads, at least one track is formed by the other magnetic head.
The present tendency is that a high-density recording technique is required, in particular, for recording analogue signals by digitization or for the manufacture of magnetic tape apparatus of smaller dimensions.
One of the methods of achieving such a high-density recording is carried out by using a rotatable head system which is currently used for video tape apparatus. Such apparatus may generally be described as types having one head, types having two heads and a 180.degree. winding, and types having four heads. Another technique, which relates to this method, is multi-track recording in which an input signal is divided into a number of channels and these channels are recorded simultaneously in a number of recording tracks. This method is used in PCM audio type apparatus with fixed heads. Moreover, the above-mentioned two techniques can be combined to obtain recording and display devices of the rotatable scanning type as suggested in U.S. Pat. No. 3,604,847.
One of the magnetic recording systems described therein, involves the use of two diametrically oppositely located magnetic heads each in the form of a stack of two single sub-heads. The sub-heads of each magnetic head are stacked so that they are at a certain distance from each other and that their transducing gaps are situated on one line. Each magnetic head forms two oblique tracks on a magnetic tape with a protective band on either side of each track, the tracks having a pitch of a track width +3 protective band widths.
As used hereinafter in the specification and claims, the word pitch will be understood to mean the distance, measured in a direction perpendicular to the oblique tracks, from the leading edge of one track to the leading edge of the other track simultaneously recorded by that head.
In case a higher density should be desired in recording, the sub-heads could be positioned so close together that no protective band is formed in between the tracks. The construction of the heads then must become different. In order to prevent cross-talk during the playback, it is necessary, in the case in which the recording has taken place without a protection band, that heads which form adjacent tracks should have different gap angles with respect to the plane of the rotatable supporting member (a plane perpendicular to the axis of rotation). This method is termed "azimuth recording". The cross-talk between adjacent tracks is prevented by the principle of azimuth loss of the recording.